1. Technical Field of the Invention
This invention most generally relates to the apparatus and methods of catheterization and related treatments of the genito-urinary and gastro-intestinal passages of mammals.
More particularly, the invention relates to a screw-based means of applying catheters, dilators and occluders to mammalian genito-urinary and gastro-intestinal passages.
2. Background Art
Urinary outlet problems most likely have been around for as long as humans.
The present state of the treatment of such problems leaves much to be desired. Intermittent catheterization must be done four to six times a day or more to service a normal rate of urine accumulation in the bladder. This repeated bodily invasion poses a high risk of infection. Patients who are determined to retain a normal degree of mobility must carry a spare catheter and cleaning supplies. They must be confident of finding greater privacy, better facilities and more time to attend to this function than non-affected persons.
The anatomy of the adult male urinary tract, as illustrated in FIG. 4, has a bladder 104 where urine is collected prior to exiting the body via the urethra 106. The bladder 104 converges into the urethra 106 at a muscular exit called the bladder neck 105. The first approximately one inch of the urethra lies within the prostate gland 107. The next approximately half inch passes through the sphincter 108, which is the muscular flow valve that controls the release of urine. The remaining six inches of the urethra lie in a spongy zone, exiting the body at the meatus 109.
The catheters of the prior art are large and stiff, difficult and uncomfortable to administer, and uncomfortable to wear for extended periods. The technique of pushing a catheter into the urethral passage requires an alternate pushing, waiting, and retracting slightly and renewing the push if the catheter is causing too much discomfort or spasmic reaction. There is a degree of skill, tolerance and patience required that takes much time, training and practice to learn. Also, long term catheterization can result in encrustation of the catheter in the bodily passage.
The difficulty, discomfort, risk of injury and infection, inhibition and inconvenience of the methods and tools of the known art results in the deprivation for many patients of the freedom to work, play and travel as do unaffected people.
History has the ancient Chinese using onion stalks to relieve people of acute urinary retention. Literature refers to such problems as far back as 206 B.C., more than 2000 years ago.
Romans used catheters, first invented by Erasistratus, a Greek doctor in the third century B.C. Roman catheters were fine tubes made of bronze. The Roman gynecologist Soranus describes how catheters could be used to push stones out of the way and back into the cavity of the bladder, and thus restore urine flow.
Excavations in Pompeii unearthed several bronze catheters. These instruments were well constructed but relatively simple and showed that designs changed little from the period 79 AD until 1700 A.D.
However, during the 17th and 18th centuries catheter construction became more complex with an intensified search for an appropriate substance that would be at once flexible, non-irritating and functional.
England, France, and the U.S.A. had individuals and companies deeply involved with urinary catheters during this period. Many variations were produced but they all caused much stress on the patient when these rigid devices were pushed into the urethra. The first practical breakthrough was by the French using gum elastic catheters--a catheter that would bend better in the urethral channel and not scour the mucosa so much in the process.
Charles Goodyear improved upon what the French produced when he successfully vulcanized crude rubber. The problem of manufacturing an instrument which was both sufficiently rigid to enable it to be pushed through the urethra into the bladder and yet flexible enough to negotiate the path, had at last reached the point of practicality, not withstanding its shortcomings.
At that time, and still to this day, a functional urethral catheter is defined as one that is flexible enough to negotiate the bends and stable enough to push through the length of the urethral passage.
The tradition use and continuing contemporary acceptance of push-to-advance catheterization may be attributed in part to the interior wall of the urethra being a series of longitudinal folds running the length of the urethra, effectively obscuring alternative means for placing the catheter.
The French urologist J. J. Cazenave, with the hopes that his country would regain leadership in the catheter field, dedicated 25-30 years of his life improving the flexible durable catheter. This was in the late 1800's and his catheter, made of decalcified ivory, was a dated device but shows the consistency of the state of the art wherein catheters are pushed into and negotiated along the urethral passage toward the bladder.
During the past 300 years or so, intensified development efforts were stimulated by professional pride, national pride and financial rewards. These efforts yielded many improvements, such as changes to size, curve shape, materials of construction, smoothness, lubricants, coatings, combinations of materials, physical properties, chemical properties and more, yet all subscribed to the basic principle of external push-to-advance.
The normal process of emptying the bladder can be interrupted by two causes. One is bladder outlet obstruction and the other is failure of the nerves linking the bladder to the brain. The most frequent cause of bladder outlet obstruction in males is enlargement of the prostate gland by hypertrophy or hyperplasia.
The prostate is a chestnut-sized gland lying inferior to the bladder and surrounding approximately the fist inch of the urethra. In older males, it is not uncommon for a progressive enlargement of the prostate to constrict the prostate urethra. This condition, known as benign prostatic hyperplasia (BPH), can cause a variety of obstructive symptoms, including urinary hesitancy, straining to void, decreased size and force of the urinary stream and in extreme cases, complete urinary retention possibly leading to renal failure.
Females, and males with no benign prostatic hyperplasia condition, might also have the inability to empty their bladder because of the nerves linking the bladder to the brain. This condition is known as neuropathic bladder, may occur in a wide variety of conditions which include spina bifida, multiple sclerosis, spinal injury, slipped disc and diabetes.
A number of irritative symptoms may also be experienced with urinary incontinence, including urinary frequency, discomfort and humiliating accidents.
Efforts to treat retention-with-overflow incontinence fall into general categories of surgical and catheterization.
Outlet obstructions resulting from BPH and Prostatic hypertropy are commonly treated by a surgical procedure known as transurethal resection. The procedure is painful, recovery is long, (about 1 year), and success is uncertain (less than 80%).
When other problems prevent the bladder from emptying effectively, catheterization is usually a solution. The two common catheterization methods are continuous and intermittent.
During continuous catheterization an indwelling catheter is retained in the bladder by a water filled balloon. It drains urine continuously from the bladder via a connecting tube into a bag which is attached to the leg or bed. The bag has a tap so that the urine can be emptied at intervals. The catheter is usually inserted by a doctor or nurse and changed about every four to six weeks.
During intermittent catheterization a simple catheter made of plastic, rubber, or metal is inserted by the patient or a helper for just long enough to empty the bladder completely, which is typically about one minute. Most patients learn to catheterize themselves and thereby gain a large degree of independence. This process is repeated about every 3-4 hours during the day and occasionally as needed at night.
In most mammals, mucous membranes line all those passages by which the internal parts communicate with the exterior, and are continuous with the skin at the various orifices of the surface of the body. They are soft and velvety, and very vascular, and their surface is coated over by their secretion, mucus, which is of a tenacious consistence, and serves to protect them from the foreign substances introduced into the body with which they are brought in contact.
They are described as lining the two tracts--the genito-urinary and the gastro-intestinal; and all, or almost all, mucous membranes may be classed as belonging to and continuous with the one or the other of these tracts. Catheterization of any of these similar bodily passages may at times be useful or necessary.
With the exception of balloon catheters, the current art of dilators has also changed little over the passage of time. A shaft with an increasing taper, bulbus structure, or enlarged end is pushed from without the passage to advance the tool through the restricted passage, thus forcing by longitudinally-applied pressure the lateral expansion of the passage walls. This push-to-advance method necessitates a stiff shaft which has all the same liabilities as traditional catheters. Catheters inherently provide a degree of this dilatorial function to the extent that the passage is opened sufficiently to accommodate the catheter.
Occluders of the prior art are similar instruments with similar liabilities; basically a bulb or plug on a shaft is inserted within a passage to provide blockage, or driven all the way into the bladder and allowed to seat as a plug at the neck of the urethra to prevent the flow of fluid from the bladder.
In summary, there are problems in making present push-in catheters stiff enough for penetration and flexible enough to make the turns without undue risk of trauma to the wall of the passageway when being pushed in; and once installed, comfortable enough to wear for an extended period. Self-administration is inhibited by all of the short-comings of the present art, and further injury, infection and discomfort may result from the resulting improper self-care.
The long history of push-in urinary catheters and the longitudinal folds of the walls of the urethra and ureter have fostered a here-to-for untested assumption that any other approach would somehow be unworkable and possibly damage or scour the mucosa further, or otherwise cause pain or distress to the subject. The soft, moist, pliant wall quite simply does not suggest a capability for providing a longitudinal grip on a threaded or helical device while allowing the sliding passage of the threads without incurring damage, but rather suggests or leads back to the traditional push-in tools and methodology.